MICRO DOSING APPARATUS WITH DIAPHRAGM FOR DETECTING A PRESSURE CHANGE IN THE LIQUID PATH

摘要

The invention concerns a micro-diaphragm (10) for forming a part of the walls of the liquid path (1) of an infusion pump for insulin which changes its shape upon a pressure change within the liquid path (1). The diaphragm (10) comprises a central area (18) which is surrounded by a deformation area (32) which in turn is surrounded by a fastening area (33). The deformation area (32) elastically interconnects the central area (18) with the fastening area (33) in order to permit a translatory movement of the central area (18) relative to the fastening area (33) upon a change of the pressure ratio between the two sides of the diaphragm (10). In a state in which both sides of the diaphragm (10) are at identical pressure, the deformation area (32) has a S-shaped cross-section and the central area (18) at one side of the diaphragm (10) at least partially protrudes over the fastening area (33) and over the deformation area (32) of the diaphragm (10). This design allows the construction of micro-diaphragms (10) which have a huge change in shape per mbar change in differential pressure over their two sides and at the same time allow for a sensitive and simple detection of this change by using the protruding central area (18) to restrict an optical path (2) passing in a plane parallel to a fastening plane of the diaphragm (10).